1. Field of the Invention
The present invention relates to method and apparatus for driving a substrate in a printing apparatus and more particularly to a method and apparatus for driving the substrate by transferring power between two members in frictional contact with the substrate.
2. Discussion of the Related Art
A typical document copier includes an electrostatic printer having a moving belt with a photoconductive surface. To transfer an image onto a sheet of paper, the printer charges the belt to a uniform potential, and subsequently exposes the belt to a pattern of light corresponding to the image. Parts of the belt exposed to the light are discharged, resulting in an electrostatic latent image being formed on the belt. The portion of the belt having the electrostatic image then passes a development station that deposits toner on the belt in the pattern of the image, resulting in a toner powder image being formed on the belt. A sheet of paper is then tacked to the belt and then removed from the belt, resulting in an image being formed on the paper.
A cleaning station removes residual toner particles that remain on the belt after the toner image has been transferred to the paper. For example, the cleaning station may include a cleaning blade that scrapes the belt to remove the residual particles from the belt.
A belt driving mechanism typically includes a motor. For good image quality, the belt driving mechanism should move the belt with substantially uniform motion. The belt, however, is subject to frictional forces, opposing the belt driving forces, from the cleaning station, for example. These opposing frictional forces may tend to promote slippage between the belt and the belt driving mechanism, causing a disruption in uniform motion of the belt.